Effect of testosterone on the apneic threshold in women during NREM sleep

Effect of obesity on sleep apnea pathogenesis differs in women versus men: multiple mediation analyses in the retrospective SNOOzzzE cohort

There are multiple mechanisms underlying obstructive sleep apnea (OSA) development. However, how classic OSA risk factors such as body mass index (BMI) and sex portend to OSA development has not been fully described. Thus we sought to evaluate how obesity leads to OSA and assess how these mechanisms differ between men and women. The San Diego Multi-Outcome OSA Endophenotype (SNOOzzzE) cohort includes 3,319 consecutive adults who underwent a clinical in-laboratory polysomnography at the University of California, San Diego, sleep clinic between January 2017 and December 2019. Using routine polysomnography signals, we determined OSA endotypes. We then performed mediation analyses stratified by sex to determine how BMI influenced the apnea-hypopnea index (AHI) using OSA pathophysiological traits as mediators, adjusting for age, race, and ethnicity. We included 2,146 patients of whom 919 (43%) were women and 1,227 (57%) were obese [body mass index (BMI) > 30 kg/m2]. BMI was significantly associated with AHI in both women and men. In men, the adjusted effect of BMI on AHI was partially mediated by a reduction in upper airway stiffness (βstandardized = 0.124), a reduction in circulatory delay (βstandardized = 0.063), and an increase in arousal threshold (βstandardized = 0.029; Pboot-strapped,all < 0.05). In women, the adjusted effect of BMI on AHI was partially mediated by a reduction in upper airway stiffness (βstandardized = 0.05) and circulatory delay (βstandardized = 0.037; Pboot-strapped,all < 0.05). BMI-related OSA pathogenesis differs by sex. An increase in upper airway collapsibility is consistent with prior studies. A reduction in circulatory delay may lead to shorter and thus more events per hour (higher AHI), while the relationship between arousal threshold and OSA is likely complex.NEW & NOTEWORTHY Our data provide important insights into obesity-related obstructive sleep apnea (OSA) pathogenesis, thereby validating, and extending, prior research findings. This is the largest sample size study to examine the relationships between obesity and gender on OSA pathogenesis. The influence of obesity on sleep apnea severity is mediated by different mechanistic traits (endotypes).

REM-OSA as a Tool to Understand Both the Architecture of Sleep and Pathogenesis of Sleep Apnea-Literature Review

Sleep is a complex physiological state, which can be divided into the non-rapid eye movement (NREM) phase and the REM phase. Both have some unique features and functions. This difference is best visible in electroencephalography recordings, respiratory system activity, arousals, autonomic nervous system activity, or metabolism. Obstructive sleep apnea (OSA) is a common condition characterized by recurrent episodes of pauses in breathing during sleep caused by blockage of the upper airways. This common condition has multifactorial ethiopathogenesis (e.g., anatomical predisposition, sex, obesity, and age). Within this heterogenous syndrome, some distinctive phenotypes sharing similar clinical features can be recognized, one of them being REM sleep predominant OSA (REM-OSA). The aim of this review was to describe the pathomechanism of REM-OSA phenotype, its specific clinical presentation, and its consequences. Available data suggest that in this group of patients, the severity of specific cardiovascular and metabolic complications is increased. Due to the impact of apneas and hypopneas predominance during REM sleep, patients are more prone to develop hypertension or glucose metabolism impairment. Additionally, due to the specific function of REM sleep, which is predominantly fragmented in the REM-OSA, this group presents with decreased neurocognitive performance, reflected in memory deterioration, and mood changes including depression. REM-OSA clinical diagnosis and treatment can alleviate these outcomes, surpassing the traditional treatment and focusing on a more personalized approach, such as using longer therapy of continuous positive airway pressure or oral appliance use.

Sleep, testosterone and cortisol balance, and ageing men

Sleep serves important biological functions, and influences health and longevity through endocrine and metabolic related systems. Sleep debt, circadian misalignment and sleep disruption from obstructive sleep apnea is widespread in modern society and accumulates with life because recovery sleep is not completely restorative. Accumulated disordered sleep throughout life impacts the ageing process and the development of age-related diseases. When epidemiological and interventional studies are considered collectively, sleep loss and lower sleep duration are associated with lower morning, afternoon and 24-h testosterone; as well as higher afternoon, but not morning or 24-h cortisol. These reciprocal changes imbalances anabolic-catabolic signaling because testosterone and cortisol are respectively the main anabolic and catabolic signals in man. Fixing testosterone-cortisol balance by means of a novel dual-hormone clamp mitigates the induction of insulin resistance by sleep restriction and provided the first proof-of-concept that the metabolic harm from sleep loss can be ameliorated by approaches that do not require sleeping more. Obstructive sleep apnea is associated with lower testosterone, even after controlling for age and obesity whereas the conclusion that continuous positive airway pressure therapy has no effect on testosterone is premature because available studies are underpowered and better-quality studies suggest otherwise. High dose testosterone therapy induces OSA, but more physiological dosing may not; and this effect may be transient or may dissipate with longer term therapy. Studies investigating the origin of the diurnal testosterone rhythm, the effect of circadian misalignment on testosterone-cortisol balance, and methods to mitigate metabolic harm, are required.

Nonalcoholic fatty liver disease and obstructive sleep apnea in women with polycystic ovary syndrome

Nonalcoholic fatty liver disease (NAFLD) and obstructive sleep apnea are frequently associated with polycystic ovary syndrome (PCOS) but remain underrecognized. Women with PCOS have a 2-4 times higher risk of NAFLD independent of body mass index than healthy weight-matched controls. Insulin resistance and hyperandrogenemia together play a central role in the pathogenesis of NAFLD. Timely diagnosis of NAFLD is important because its progression can lead to nonalcoholic steatohepatitis and/or advanced liver fibrosis that can eventually result in liver-related mortality. The presence of NAFLD has also been associated with increased risks of type 2 diabetes, cardiovascular events, overall mortality, and extrahepatic cancers. The treatment of NAFLD in PCOS should include lifestyle interventions. Glucagon-like peptide 1 receptor agonists have shown promising results in patients with PCOS and NAFLD, but future randomized trails are needed to confirm this benefit. Likewise, the use of combined oral estrogen-progestin contraceptives may provide a benefit by decreasing hyperandrogenemia. Sleep disordered breathing is common among women with PCOS and is responsible for a number of cardiometabolic derangements. Obstructive sleep apnea is most often found in overweight and obese women with PCOS, but as is the case with NAFLD, its prevalence exceeds that of women who are of similar weight without PCOS. Left untreated, obstructive sleep apnea can precipitate or exacerbate insulin resistance, glucose intolerance, and hypertension.

Neurological effects of respiratory dysfunction

The respiratory and the nervous systems are closely interconnected and are maintained in a fine balance. Central mechanisms maintain strict control of ventilation due to the high metabolic demands of brain which depends on a continuous supply of oxygenated blood along with glucose. Moreover, brain perfusion is highly sensitive to changes in the partial pressures of carbon dioxide and oxygen in blood, which in turn depend on respiratory function. Ventilatory control is strictly monitored and regulated by the central nervous system through central and peripheral chemoreceptors, baroreceptors, the cardiovascular system, and the autonomic nervous system. Disruption in this delicate control of respiratory function can have subtle to devastating neurological effects as a result of ensuing hypoxia or hypercapnia. In addition, pulmonary circulation receives entire cardiac output and this may act as a conduit to transmit infections and also for metastasis of malignancies to brain resulting in neurological dysfunction. Furthermore, many neurological paraneoplastic syndromes can have underlying lung malignancies resulting in respiratory dysfunction. It is essential to understand the underlying mechanisms and the resulting manifestations in order to prevent and effectively manage the many neurological effects of respiratory dysfunction. This chapter explores the various neurological effects of respiratory dysfunction with focus on their pathophysiology, etiologies, clinical features and long-term neurological sequelae.

Central sleep apnea

Central apnea syndrome is a disorder with protean manifestations and concomitant conditions. It can occur as a distinct clinical entity or as part of another clinical syndrome. The pathogenesis of central sleep apnea (CSA) varies depending on the clinical condition. Sleep-related withdrawal of the ventilatory drive to breathe is the common denominator among all cases of central apnea, whereas hypocapnia is the final common pathway leading to apnea in the majority of central apnea. Medical conditions most closely associated with CSA include heart failure, stroke, spinal cord injury, and opioid use, among others. Nocturnal polysomnography is the standard diagnostic method, including measurement of sleep and respiration. The latter includes detection of flow, measurement of oxyhemoglobin saturation and detection of respiratory effort. Management strategy incorporates clinical presentation, associated conditions, and the polysomnographic findings in an individualized manner. The pathophysiologic heterogeneity may explain the protean clinical manifestations and the lack of a single effective therapy for all patients. While research has enhanced our understanding of the pathogenesis of central apnea, treatment options are extrapolated from treatment of obstructive sleep apnea. Co-morbid conditions and concomitant obstructive sleep apnea influence therapeutic approach significantly. Therapeutic options include positive pressure therapy, pharmacologic therapy, and supplemental Oxygen. Continuous positive airway pressure (CPAP) is the initial standard of care, although the utility of other modes of positive pressure therapy, as well as pharmacotherapy and device-based therapies, are currently being investigated.

Sleep Habits of Women With Infertility

CONTEXT

Sleep plays important roles in metabolic and reproductive function, and polycystic ovary syndrome (PCOS) is associated with sleep disturbances, including increased prevalence of obstructive sleep apnea.

OBJECTIVE

We sought to evaluate sleep parameters in infertile women with PCOS compared with women with unexplained infertility (UI) and identify risk factors for disturbed sleep.

METHODS

At private and academic ambulatory gynecology and infertility practices, we evaluated a prospective cohort of women diagnosed with PCOS or UI from 2 randomized clinical trials. We included 1603 infertile women enrolled in 2 concurrent randomized clinical trials. The main outcome measures were self-reported sleep measures.

RESULTS

Sleep duration <6 hours (6.1% vs 2.7%; P < .001), habitual snoring (37.8% vs 19.0%; P < .001), and clinical sleepiness (12.0% vs 8.6%; P < .026) were more common in women with PCOS than those with UI. After adjusting for covariates, PCOS and elevated fasting insulin were associated (P = .010) with clinical symptoms of obstructive sleep apnea (OSA) diagnosis, whereas PCOS, elevated insulin (P = .003), WC >88 cm (P = .003), and current smoking (P = .012) were associated with habitual snoring. Clinical depression score (P < .001) and PCOS diagnosis (P = .002) were associated with perceived daytime sleepiness. Short sleep duration and clinical symptoms of OSA were not associated with conception and live birth rates.

CONCLUSION

Infertile women with PCOS more commonly report sleep disturbances than those with UI. Markers of insulin resistance are associated with previous diagnosis of OSA, habitual snoring, and short sleep duration. The presence of clinical symptoms of OSA or short sleep duration does not affect fertility treatment response.

Obesity and polycystic ovary syndrome

The increased global prevalence of obesity over the last 40-years has driven a rise in prevalence of obesity-related co-morbidities, including polycystic ovary syndrome (PCOS). On a background of genetic susceptibility, PCOS often becomes clinically manifest following weight gain, commonly during adolescence. A common endocrinopathy affecting between 6%-10% of reproductive-age women, PCOS presents with the cardinal features of hyperandrogenism, reproductive and metabolic dysfunction. PCOS associates with insulin resistance, independently of (but amplified by) obesity. Insulin resistance in PCOS is characterized by abnormal post-receptor signalling within the phosphatidylinositol-kinase (PI3-K) pathway. Multiple factors (including most notably, weight gain) contribute towards the severity of insulin resistance in PCOS. Compensatory hyperinsulinaemia ensues, resulting in over-stimulation of the (intact) post-receptor mitogen-activated protein kinase (MAP-K) insulin pathway, with consequent implications for steroidogenesis and ovarian function. In this concise review, we explore the effects of weight gain and obesity on the pathogenesis of PCOS from the perspective of its three cardinal features of hyperandrogenism, reproductive and metabolic dysfunction, with a focus on the central mediating role of the insulin pathway. We also consider key lifestyle strategies for the effective management of obese and overweight women with PCOS.

Central Sleep Apnea

Central sleep apnea (CSA) is characterized by intermittent repetitive cessation and/or decreased breathing without effort caused by an abnormal ventilatory drive. Although less prevalent than obstructive sleep apnea, it is frequently encountered. CSA can be primary (idiopathic) or secondary in association with Cheyne-Stokes respiration, drug-induced, medical conditions such as chronic renal failure, or high-altitude periodic breathing. Risk factors have been proposed, including gender, age, heart failure, opioid use, stroke, and other chronic medical conditions. This article discusses the prevalence of CSA in the general population and within each of these at-risk populations, and clinical presentation, diagnostic methods, and treatment.

Research Priorities for Patients with Heart Failure and Central Sleep Apnea. An Official American Thoracic Society Research Statement

Background: Central sleep apnea (CSA) is common among patients with heart failure and has been strongly linked to adverse outcomes. However, progress toward improving outcomes for such patients has been limited. The purpose of this official statement from the American Thoracic Society is to identify key areas to prioritize for future research regarding CSA in heart failure.

Methods: An international multidisciplinary group with expertise in sleep medicine, pulmonary medicine, heart failure, clinical research, and health outcomes was convened. The group met at the American Thoracic Society 2019 International Conference to determine research priority areas. A statement summarizing the findings of the group was subsequently authored using input from all members.

Results: The workgroup identified 11 specific research priorities in several key areas: 1) control of breathing and pathophysiology leading to CSA, 2) variability across individuals and over time, 3) techniques to examine CSA pathogenesis and outcomes, 4) impact of device and pharmacological treatment, and 5) implementing CSA treatment for all individuals

Conclusions: Advancing care for patients with CSA in the context of heart failure will require progress in the arenas of translational (basic through clinical), epidemiological, and patient-centered outcome research. Given the increasing prevalence of heart failure and its associated substantial burden to individuals, society, and the healthcare system, targeted research to improve knowledge of CSA pathogenesis and treatment is a priority.

Treatment-Emergent Central Apnea: Physiologic Mechanisms Informing Clinical Practice

The purpose of this review was to describe our management approach to patients with treatment-emergent central sleep apnea (TECSA). The emergence of central sleep apnea during positive airway pressure therapy occurs in approximately 8% of titration studies for OSA, and it has been associated with several demographic, clinical, and polysomnographic factors, as well as factors related to the titration study itself. TECSA shares similar pathophysiology with central sleep apnea. In fact, central and OSA pathophysiologic mechanisms are inextricably intertwined, with ventilatory instability and upper airway narrowing occurring in both entities. TECSA is a "dynamic" process, with spontaneous resolution with ongoing positive airway pressure therapy in most patients, persistence in some, or appearing de novo in a minority of patients. Management strategy for TECSA aims to eliminate abnormal respiratory events, stabilize sleep architecture, and improve the underlying contributing medical comorbidities. CPAP therapy remains a standard therapy for TECSA. Expectant management is appropriate given its transient nature in most cases, whereas select patients would benefit from an early switch to an alternative positive airway pressure modality. Other treatment options include supplemental oxygen and pharmacologic therapy.

Prevalent and sex-biased breathing patterns modify functional connectivity MRI in young adults

Resting state functional connectivity magnetic resonance imaging (fMRI) is a tool for investigating human brain organization. Here we identify, visually and algorithmically, two prevalent influences on fMRI signals during 440 h of resting state scans in 440 healthy young adults, both caused by deviations from normal breathing which we term deep breaths and bursts. The two respiratory patterns have distinct influences on fMRI signals and signal covariance, distinct timescales, distinct cardiovascular correlates, and distinct tendencies to manifest by sex. Deep breaths are not sex-biased. Bursts, which are serial taperings of respiratory depth typically spanning minutes at a time, are more common in males. Bursts share features of chemoreflex-driven clinical breathing patterns that also occur primarily in males, with notable neurological, psychiatric, medical, and lifespan associations. These results identify common breathing patterns in healthy young adults with distinct influences on functional connectivity and an ability to differentially influence resting state fMRI studies.

Functional connectivity measured from fMRI data is widely used in neuroscience. Here the authors report an association between two types of breathing signature and obtained BOLD data, and associated sex differences.

A Clinical Perspective of Sleep and Andrological Health: Assessment, Treatment Considerations, and Future Research

CONTEXT

Sleep that is insufficient, misaligned, or disrupted causes hypersomnolence and neuropsychological deficits, adversely affects cardiometabolic health, and is increasingly recognized to impair other biological processes that lead to conditions important to men, such as hypogonadism, erectile dysfunction, and infertility.

EVIDENCE ACQUISITION

Literature review from 1970 to December 2018.

EVIDENCE SYNTHESIS

High-quality and complementary epidemiological and interventional studies establish that abnormal sleep is associated with increased mortality, hypertension, and other cardiometabolic disorders (insufficient, disrupted, and misaligned sleep), as well as reduced fecundity and total sperm count (insufficient sleep), erectile dysfunction (disrupted sleep), and low testosterone (both). Circadian misalignment shifts the peak of testosterone's diurnal rhythm to occur soon after waking up, irrespective of the biological clock time, but it does not change the mean concentration. Preliminary studies show that extending sleep in individuals who are chronically sleep deprived may become a strategy to reduce insulin resistance and hypertension. Continuous positive airway pressure therapy can improve erectile function, and possibly systemic testosterone exposure, but only when used adherently by men with obstructive sleep apnea. Both high-dose and replacement-dose testosterone therapies modestly worsen sleep-disordered breathing, but they also improve cardiometabolic function and sexual desire. Persistence of either the adverse or beneficial outcomes over the longer term requires further investigation.

CONCLUSIONS

Sleep is increasingly recognized to be essential for healthy living. Establishing the effect of abnormal sleep, and of improving sleep, on andrological issues of prime interest to men will promote prioritization of sleep, and may thereby improve overall long-term health outcomes.

Obesity and Polycystic Ovary Syndrome: Implications for Pathogenesis and Novel Management Strategies

Polycystic ovary syndrome (PCOS) is a common female condition typified by reproductive, hyperandrogenic, and metabolic features. Polycystic ovary syndrome is a genetic condition, exacerbated by obesity. There is a close link between obesity and PCOS based on epidemiological data, and more recently corroborated through genetic studies. There are many mechanisms mediating the effects of weight-gain and obesity on the development of PCOS. The metabolic effects of insulin resistance and steroidogenic and reproductive effects of hyperinsulinaemia are important mechanisms. Adipokine production by subcutaneous and visceral fat appears to play a part in metabolic function. However, given the complexity of PCOS pathogenesis, it is important also to consider possible effects of PCOS on further weight-gain, or at least on hampering attempts at weight-loss and maintenance through lifestyle changes. Possible mediators of these effects include changes in energy expenditure, mental ill health, or physical inactivity. In this brief review, we discuss the main mechanisms that underlie the association between obesity and PCOS, from divergent perspectives of weight-gain contributing to development of PCOS and vice versa. We also consider novel management options for women with obesity and PCOS.

Unstable control of breathing can lead to ineffective noninvasive ventilation in amyotrophic lateral sclerosis

Upper airway obstruction with decreased central drive (ODCD) is one of the causes of ineffective noninvasive ventilation (NIV) in amyotrophic lateral sclerosis (ALS). The aim of this study is to determine the mechanism responsible for ODCD in ALS patients using NIV.

This is a prospective study that included ALS patients with home NIV. Severity of bulbar dysfunction was assessed with the Norris scale bulbar subscore; data on upper or lower bulbar motor neuron predominant dysfunction on physical examination were collected. Polysomnography was performed on every patient while using NIV and the ODCD index (ODCDI: number of ODCD events/total sleep time) was calculated. To determine the possible central origin of ODCD, controller gain was measured by inducing a hypocapnic hyperventilation apnoea. Sonography of the upper airway during NIV was performed to determine the location of the ODCD.

30 patients were enrolled; three (10%) had ODCDI >5 h⁻¹. The vast majority of ODCD events were produced during non-rapid eye movement sleep stages and were a consequence of an adduction of the vocal folds. Patients with ODCDI >5 h⁻¹ had upper motor neuron predominant dysfunction at the bulbar level, and had greater controller gain (1.97±0.33 versus 0.91±0.36 L·min⁻¹·mmHg⁻¹; p<0.001) and lower carbon dioxide (CO₂) reserve (4.00±0.00 versus 10.37±5.13 mmHg; p=0.043). ODCDI was correlated with the severity of bulbar dysfunction (r= −0.37; p=0.044), controller gain (r=0.59; p=0.001) and CO₂ reserve (r= −0.35; p=0.037).

ODCD events in ALS patients using NIV have a central origin, and are associated with instability in the control of breathing and an upper motor neuron predominant dysfunction at the bulbar level.

Upper airway obstructions in ALS patients using NIV have a central origin, and are associated with instability in the control of breathing and an upper motor neuron predominant dysfunction at the bulbar levelhttp://bit.ly/2WEMt28

Sleep disorders in polycystic ovary syndrome: influence of obesity and hyperandrogenism

OBJECTIVE

This study aims to evaluate the sleep of subjects with polycystic ovary syndrome (PCOS), with and without hyperandrogenism, in comparison with a healthy control group and examine the effects of hyperandrogenism and obesity on sleep parameters.

METHODS

A total of 44 volunteers were recruited to participate in the study. Clinical, biochemical and polysomnographic parameters were used to diagnose PCOS and hyperandrogenism. The evaluation of sleep quality was made using validated questionnaires and polysomnography test. The frequency of obstructive sleep apnea was also compared between the groups.

RESULTS

The study revealed that women with PCOS presented poorer subjective sleep quality, increased incidence of snoring and a higher risk of obstructive sleep apnea, based on the Berlin questionnaire. Also, after adjusting for body mass index, PCOS subjects had rapid eye movement (REM) time lower than those in the control group. PCOS women versus those without hyperandrogenism did not differ on any sleep measurement. Women with obstructive sleep apnea were only diagnosed in the PCOS group.

CONCLUSIONS

Our results indicate that PCOS impairs subjective sleep quality, as well as objective sleep quality, due to a reduction in REM sleep stage time in women diagnosed with the syndrome. Obesity affected sleep-related parameters but hyperandrogenism had no effect. Only the PCOS group had obstructive sleep apnea diagnosis.

Periodic breathing in healthy young adults in normobaric hypoxia equivalent to 3500 m, 4500 m, and 5500 m altitude

Purpose

The occurrence of periodic breathing (PB) at high altitude during sleep and the quality of sleep are individually different and influenced by multiple factors including sex. Although poor sleep quality at high altitude might not be directly linked to oxygen desaturations, the PB upsurge at high altitude leads to significant oscillations in oxygen saturation.

Methods

Thirty-three students were recruited. Participants were randomly assigned to three groups (A, B, C) sleeping one full night in a dormitory with normobaric hypoxia at a F_IO2 of 14.29% (A), a F_IO2 of 12.47% (B), or a F_IO2 of 10.82% (C). Full polysomnography was performed in each participant.

Results

Mean total sleeping time decreased significantly with increasing hypoxia (p < 0.001). Respiratory events changed from central hypopneas to central apneas (CA) with increasing hypoxia: CA = 17.8%, 50.0%, 92.2% of AHI (37.96 events per hour (n/h), 68.55 n/h, 93.44 n/h). AHI (p = 0.014) and time duration of respiratory events (p = 0.003) were significantly different between sexes, both greater in men. REM sleep was reduced.

Conclusions

Men tend to be more prone to PB in normobaric hypoxia. Further research should implicate a longer acclimatization period around simulated 4500 m in order to find out if the exponential increase in PB between 4500 m and 5500 m could be shifted to lower hypoxic levels, i.e., higher altitudes.

The Importance of Sleep Hygiene in Polycystic Ovary Syndrome from the View of Iranian Traditional Medicine and Modern Medicine

Polycystic ovary syndrome (PCOS) is known as the most common hormonal disorder in women at reproductive age. Recent studies have revealed a high prevalence of sleep disorders in PCOS, suggesting that it is an amendable factor for these patients; however, the sleep was not considered in their treatment plan. According to the Iranian traditional medicine (ITM), sleep is an important item in the lifestyle modification of all diseases. The aim of this study is to determine the importance of sleep hygiene in PCOS from the view of ITM and Modern Medicine. In this study, some keywords about “sleep and PCOS” were searched in medical databases and some ITM books. Lifestyle modification is one of the first steps in treatment of patients with PCOS in which the emphasis will be mainly on exercise and diet. Despite proof of the high prevalence of sleep disorders in these patients, modification of sleep is not considered in their lifestyle. ITM as a holistic medicine emphasizes on lifestyle modification under the title of “Settah-e-Zaruria” (In Persian), the six essential schemes for the prevention and treatment of all diseases. Management of sleep is one of these schemes. There are many advices about sleep hygiene in both ITM and modern medicine. It seems that lifestyle modification should be expanded in PCOS patients to include more options, and sleep hygiene should be considered in their lifestyle alongside food and exercise.

Determinants of Slow-Wave Activity in Overweight and Obese Adults: Roles of Sex, Obstructive Sleep Apnea and Testosterone Levels

Background: Slow-wave activity (SWA) in non-rapid eye movement (NREM) sleep, obtained by spectral analysis of the electroencephalogram, is a marker of the depth or intensity of NREM sleep. Higher levels of SWA are associated with lower arousability during NREM sleep and protect against sleep fragmentation. Multiple studies have documented that SWA levels are higher in lean women, compared to age-matched lean men, but whether these differences persist in obese subjects is unclear. Obstructive sleep apnea (OSA), a condition associated with obesity, is more prevalent in men than in women. Sex differences in SWA could therefore be one of the factors predisposing men to OSA. Furthermore, we hypothesized that higher levels of testosterone may be associated with lower levels of SWA. Objective: The aim of the current study was to identify sex differences in the determinants of SWA in young and middle-aged overweight and obese adults. Methods: We enrolled 101 overweight and obese but otherwise healthy participants from the community (44 men, 57 women) in this cross-sectional study. Participants underwent an overnight in-laboratory polysomnogram. The recordings were submitted to sleep staging and spectral analysis. Sex differences and the potential contribution of testosterone levels were evaluated after adjusting for age, body mass index and race/ethnicity. Results: OSA was present in 66% of men and in 44% of women. After adjustment for differences in age, race/ethnicity and BMI, the odds ratio for OSA in men vs. women was 3.17 (95% CI 1.14-9.43, p = 0.027). There was a graded inverse relationship between the apnea-hypopnea index (AHI) and SWA in men (β = -0.21, p = 0.018) but not in women (β = 0.10, p = 0.207). In a multivariate regression model, higher testosterone levels were independently associated with lower SWA in men after controlling for age, race/ethnicity and apnea-hypopnea index (β = -0.56, p = 0.025). Conclusion: Increasing severity of OSA was associated with significant decrease in sleep intensity in men but not in women. Higher testosterone levels were associated with lower sleep intensity in men. Men with higher testosterone levels may therefore have lower arousal thresholds and higher ventilatory instability in NREM sleep, and be at greater risk of OSA.

Aging is associated with increased propensity for central apnea during NREM sleep

The reason for increased sleep-disordered breathing with predominance of central apneas in the elderly is unknown. We hypothesized that the propensity to central apneas is increased in older adults, manifested by a reduced carbon-dioxide (CO₂) reserve in older compared with young adults during non-rapid eye movement sleep. Ten elderly and 15 young healthy adults underwent multiple brief trials of nasal noninvasive positive pressure ventilation during stable NREM sleep. Cessation of mechanical ventilation (MV) resulted in hypocapnic central apnea or hypopnea. The CO₂ reserve was defined as the difference in end-tidal CO₂ ([Formula: see text]) between eupnea and the apneic threshold, where the apneic threshold was [Formula: see text] that demarcated the central apnea closest to the eupneic [Formula: see text]. For each MV trial, the hypocapnic ventilatory response (controller gain) was measured as the change in minute ventilation (V̇e) during the MV trial for a corresponding change in [Formula: see text]. The eupneic [Formula: see text] was significantly lower in elderly vs. young adults. Compared with young adults, the elderly had a significantly reduced CO₂ reserve (-2.6 ± 0.4 vs. -4.1 ± 0.4 mmHg, P = 0.01) and a higher controller gain (2.3 ± 0.2 vs. 1.4 ± 0.2 l·min^-1·mmHg^-1, P = 0.007), indicating increased chemoresponsiveness in the elderly. Thus elderly adults are more prone to hypocapnic central apneas owing to increased hypocapnic chemoresponsiveness during NREM sleep. NEW & NOTEWORTHY The study describes an original finding where healthy older adults compared with healthy young adults demonstrated increased breathing instability during non-rapid eye movement sleep, as suggested by a smaller carbon dioxide reserve and a higher controller gain. The findings may explain the increased propensity for central apneas in elderly adults during sleep and potentially guide the development of pathophysiology-defined personalized therapies for sleep apnea in the elderly.

Polycystic ovary syndrome and the risk of obstructive sleep apnea: a meta-analysis and review of the literature

BACKGROUND AND OBJECTIVE

Polycystic ovary syndrome (PCOS) has been reported to be associated with the development of obstructive sleep apnea (OSA). The objective of this meta-analysis is to assess the relationship between PCOS and OSA.

METHODS

A literature search was conducted to identify studies linking PCOS with the risk of OSA. Studies in which the presence of OSA was confirmed with overnight polysomnography were included. Random effects models were used to calculate pooled relative risks.

RESULTS

Eight studies conducted in adults and five studies conducted in adolescents were identified. The pooled OSA prevalence was 0.22 (95% confidence interval (CI): 0.08-0.40) in PCOS patients. The pooled prevalence of OSA was higher in adults (0.32, 95% CI: 0.13-0.55) than adolescents (0.08, 95% CI: 0.00-0.30). Risk of OSA was significantly increased in adult patients with PCOS (odds ratio (OR) 9.74, 95% CI: 2.76-34.41). Risk of OSA was not significantly increased in adolescents (OR: 4.54, 95% CI:0.56-36.43).

CONCLUSIONS

These findings demonstrate a significant association between PCOS and OSA in adult patients. Considering the increased risk for long-term cardiometabolic disorders associated with both PCOS and OSA, it is important to diagnose and treat OSA in patients with PCOS.

Central Sleep Apnea in Patients with Congestive Heart Failure

Central sleep apnea and Cheyne-Stokes respiration are commonly observed breathing patterns during sleep in patients with congestive heart failure. Common risk factors are male gender, older age, presence of atrial fibrillation, and daytime hypocapnia. Proposed mechanisms include augmented peripheral and central chemoreceptor sensitivity, which increase ventilator instability during both wakefulness and sleep; diminished cerebrovascular reactivity and increased circulation time, which impair the normal buffering of Paco₂ and hydrogen ions and delay the detection of changes in Paco₂ during sleep; and rostral fluid shifts that predispose to hypocapnia.

A Practical Approach to the Identification and Management of Sleep-Disordered Breathing in Heart Failure Patients

Sleep-disordered breathing (SDB) is a major health problem affecting much of the general population. Although SDB is responsible for rapid progression of heart failure (HF) and the worsening morbidity and mortality, advanced HF state is associated with accelerated development of SDB. In the face of recent developments in SDB treatment and availability of effective therapeutic options known to improve quality of life, exercise tolerance, and heart function, most HF patients with SDB are left unrecognized and untreated. This article provides an overview of SDB in HF with focus on practical approaches intended to facilitate screening and treatment.

Control of Ventilation in Health and Disease

Control of ventilation occurs at different levels of the respiratory system through a negative feedback system that allows precise regulation of levels of arterial carbon dioxide and oxygen. Mechanisms for ventilatory instability leading to sleep-disordered breathing include changes in the genesis of respiratory rhythm and chemoresponsiveness to hypoxia and hypercapnia, cerebrovascular reactivity, abnormal chest wall and airway reflexes, and sleep state oscillations. One can potentially stabilize breathing during sleep and treat sleep-disordered breathing by identifying one or more of these pathophysiological mechanisms. This review describes the current concepts in ventilatory control that pertain to breathing instability during wakefulness and sleep, delineates potential avenues for alternative therapies to stabilize breathing during sleep, and proposes recommendations for future research.

Sex differences in sleep disordered breathing in adults

The prevalence of sleep disordered breathing is greater in men compared to women. This disparity could be due to sex differences in the diagnosis and presentation of sleep apnea, and the pathophysiological mechanisms that instigate this disorder. Women tend to report more non-typical symptoms of sleep apnea compared to men, and the presentation of apneic events are more prevalent in rapid compared to non-rapid eye movement sleep. In addition, there is evidence of sex differences in upper airway structure and mechanics and in neural mechanisms that impact on the control of breathing. The purpose of this review is to summarize the literature that addresses sex differences in sleep-disordered breathing, and to discuss the influence that upper airway mechanics, chemoreflex properties, and sex hormones have in modulating breathing during sleep in men and women.

Obesity may be the common pathway for sleep-disordered breathing in women with polycystic ovary syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is one of the most common endocrinological disorders in women of reproductive age, and is characterized by hyperandrogenism. It is associated with long-term metabolic dysfunctions including sleep-disordered breathing (SDB). We hypothesized that the increased prevalence of SDB in PCOS results from raised testosterone levels.

METHODS

This was a prospective, cross-sectional, case-control study in which 50 case patients with untreated PCOS and 100 control subjects were included. All the case patients and control subjects went through a detailed clinical, biochemical, and hormonal evaluation. Overnight polysomnography was performed in all case patients and the snorers (16 of 100) in the control group.

RESULTS

SDB was seen in 66% of the case patients and in 4% of control group with (odds ratio [OR] = 46.5, 95% confidence interval [CI] = 14.6-148.4; p <0.001). After adjustment for body mass index (BMI) and waist circumference (WC), the difference was not significant (p = 0.993 and p = 0.931, respectively). The SDB patients with PCOS showed significantly higher respiratory distress index (RDI) values than SDB patients in the control group (22.5 ± 21.5 vs 9.0 ± 5.6, p = 0.01). On the Epworth Sleepiness Scale the PCOS case patients reported feeling more sleepy than did the control subjects (12.5 ± 3.2 vs 9.32 ± 1.7, p <0.001). Free testosterone levels were also significantly higher in the PCOS group than in the control subjects (2.95 ± 3.44 vs 1.5 ± 1.0, p <0.001). There was a significant correlation between free testosterone level and RDI values (r = 0.377; p = 0.007), WC (r = 0.315; p = 0.026), and BMI (r = 0.398; p = 0.004). A significant correlation of WC (r = 0.551; p <0.001) and BMI (r = 0.572; p <0.001) was observed with RDI.

CONCLUSION

Testosterone-induced obesity is probably the common pathway for the development of SDB in PCOS.

Obstructive sleep apnea predisposes to nonalcoholic Fatty liver disease in patients with polycystic ovary syndrome

OBJECTIVE

Some studies have shown a higher prevalence of nonalcoholic fatty liver disease (NAFLD) and obstructive sleep apnea (OSA) in patients with polycystic ovary syndrome (PCOS). The objective of this study was to assess NAFLD in PCOS women with and without OSA. A possible role of high serum androgen levels in the development of OSA in PCOS women was also investigated.

METHODS

Biochemical, hormonal, and polysomnography parameters were determined in 38 premenopausal PCOS patients. NAFLD was evaluated by ultrasound. Testosterone was measured by an immunoassay.

RESULTS

Serum androgen levels and the prevalence of NAFLD (83.3% vs. 26.9%; P<.001) were higher in patients with OSA than those without OSA. The mean apnea-hypopnea index (AHI) was higher in patients with NAFLD than in those without NAFLD (16.87 events [ev]/h vs. 1.57 ev/h; P<.002). On multivariate logistic regression, where body mass index ≥30 kg/m2, homeostasis model assessment for insulin resistance ≥2.7, and OSA (AHI ≥5 ev/h) were independent variables, only OSA was an independent predictor of NAFLD (odds ratio [OR], 7.63; P = .044). Free testosterone levels ≥1.07 ng/dL were also independently associated with OSA (OR, 8.18; P = .023).

CONCLUSION

In PCOS women, the occurrence of OSA strongly predisposes them to development of NAFLD and a worse metabolic profile; hence, treatment of OSA might be beneficial for NAFLD.

Reduced respiratory neural activity elicits a long-lasting decrease in the CO2 threshold for apnea in anesthetized rats

Two critical parameters that influence breathing stability are the levels of arterial pCO₂ at which breathing ceases and subsequently resumes - termed the apneic and recruitment thresholds (AT and RT, respectively). Reduced respiratory neural activity elicits a chemoreflex-independent, long-lasting increase in phrenic burst amplitude, a form of plasticity known as inactivity-induced phrenic motor facilitation (iPMF). The physiological significance of iPMF is unknown. To determine if iPMF and neural apnea have long-lasting physiological effects on breathing, we tested the hypothesis that patterns of neural apnea that induce iPMF also elicit changes in the AT and RT. Phrenic nerve activity and end-tidal CO₂ were recorded in urethane-anesthetized, ventilated rats to quantify phrenic nerve burst amplitude and the AT and RT before and after three patterns of neural apnea that differed in their duration and ability to elicit iPMF: brief intermittent neural apneas, a single brief "massed" neural apnea, or a prolonged neural apnea. Consistent with our hypothesis, we found that patterns of neural apnea that elicited iPMF also resulted in changes in the AT and RT. Specifically, intermittent neural apneas progressively decreased the AT with each subsequent neural apnea, which persisted for at least 60min. Similarly, a prolonged neural apnea elicited a long-lasting decrease in the AT. In both cases, the magnitude of the AT decrease was proportional to iPMF. In contrast, the RT was transiently decreased following prolonged neural apnea, and was not proportional to iPMF. No changes in the AT or RT were observed following a single brief neural apnea. Our results indicate that the AT and RT are differentially altered by neural apnea and suggest that specific patterns of neural apnea that elicit plasticity may stabilize breathing via a decrease in the AT.

Comparison of clinical features and polysomnographic findings between men and women with sleep apnea

BACKGROUND

There is a scarcity of reports comparing gender differences in polysomnographic findings among Asian patients with sleep apnea (SA). In this study, we elucidated gender differences in the clinical features and polysomnographic findings of SA patients in Japan.

METHODS

We conducted a case-matched control study to compare the gender differences. A total of 4,714 patients (4,127 men; 587 women) were matched for age, apnea-hypopnea index (AHI), and body mass index (BMI). The criteria used for sex matching were (I) age ±4 years, (II) AHI ± 4 h of sleep, and (III) BMI ±2 kg/m(2). This facilitated the comparison of polysomnography sleep variables in 296 men and 296 women with SA.

RESULTS

Compared with their male counterparts, female SA patients had a significantly higher rapid eye movement AHI [men: 27.7 (IQR, 14.3-45.2); women: 43.3 (IQR, 25.5-56.6); P<0.001], lower supine AHI [men: 29.7 (IQR, 16.8-49.5); women: 25.0 (IQR, 14.7-39.3); P=0.004], longer total sleep time (TST), and non-rapid eye movement (NREM) sleep stage 3 (N3), %TST [TST in men: 356.3 (IQR, 319.5-392.3); women: 372.0 (IQR, 327.8-404.5); P=0.007; N3, %TST in men: 8.8 (IQR, 3.0-14.6); women: 14.4 (IQR, 8.3-20.4); P<0.001], and better sleep efficiency [men: 80.9 (IQR, 71.0-88.0); women: 83.2 (IQR, 74.5-90.0); P=0.011].

CONCLUSIONS

This study revealed that women with SA had a significantly longer TST and N3, %TST, which represents deep sleep. Future prospective studies must be conducted together with polysomnography tests including electromyography of pharyngeal muscle expansion and electroencephalography.

Sleep disordered breathing: is it different for females?

Obstructive sleep apnoea (OSA) is no longer considered to be a disease of males only. The latest prevalence estimates of moderate-to-severe OSA in women range from 6% to 20% [1, 2], resulting in male/female ratio from 3/1 to 2/1 [1]. These figures may still underestimate the prevalence of sleep disordered breathing (SDB) in women, in whom the upper airway obstruction often manifests as noncountable, nonapnoeic respiratory events (snoring, flow limitation or partial upper airway obstruction) [3–6]. Failure to recognise the distinct clinical presentation and partial obstruction in sleep studies may lead to under-recognition of SDB in females [7, 8]. For instance, prior to diagnosing OSA, women are twice as likely as men to be treated for depression [7].

Predominance of low AHI and partial upper airway obstruction may lead to undertreatment of female SDBhttp://ow.ly/TKN7d

Contemporary insights and novel treatment approaches to central sleep apnea syndrome in heart failure

OPINION STATEMENT

Central sleep apnea (CSA) is a common and under-diagnosed condition commonly associated with Cheyne-Stokes respiration. It is particularly prevalent in the heart failure population affecting up to 40 % of all patients with heart failure. The pathophysiology associated with CSA is based on the underlying effects of hypoventilation and hyperventilation, with neurologic dysregulation of respiratory control as the primary defect. However, therapeutic options are limited because of the prevailing perception that CSA is a consequence, rather than cause of morbidity and mortality. At present, the main focus remains treating the underlying problem (ie, intensifying heart failure therapeutics, decongestion), whereas additional suggestions of using acetazolamide, progesterone, nocturnal oxygen, and theophylline have not been validated with contemporary clinical trials. Positive pressure ventilation is currently the primary recommendation for all patients with sleep-disordered breathing (CSA included), and in some patients may effectively reduce the apnea-hypopnea index. However, significant research is ongoing to determine how to treat this complex patient population.

Leptin deficiency promotes central sleep apnea in patients with heart failure

BACKGROUND

Leptin-deficient animals hyperventilate. Leptin expression by adipocytes is attenuated by atrial natriuretic peptide (ANP). Increased circulating natriuretic peptides (NPs) are associated with an increased risk of central sleep apnea (CSA). This study tested whether serum leptin concentration is inversely correlated to NP concentration and decreased in patients with heart failure (HF) and CSA.

METHODS

Subjects with HF (N = 29) were studied by measuring leptin, NPs, CO2 chemosensitivity (Δminute ventilation [V.e]/Δpartial pressure of end-tidal CO2 [Petco2]), and ventilatory efficiency (V.e/CO2 output [V.co2]) and were classified as CSA or no sleep-disordered breathing by polysomnography. CSA was defined as a central apnea-hypopnea index ≥ 15. The Student t test, Mann-Whitney U test, and logistic regression were used for analysis, and data were summarized as mean ± SD; P &lt; .05 was considered significant.

RESULTS

Subjects with CSA had higher ANP and brain natriuretic peptide (BNP) concentrations (P &lt; .05), ΔV.e/ΔPetco2 (2.39 ± 1.03 L/min/mm Hg vs 1.54 ± 0.35 L/min/mm Hg, P = .01), and V.e/V.co2 (43 ± 9 vs 34 ± 7, P &lt; .01) and lower leptin concentrations (8 ± 10.7 ng/mL vs 17.1 ± 8.8 ng/mL, P &lt; .01). Logistic regression analysis (adjusted for age, sex, and BMI) demonstrated leptin (OR = 0.07; 95% CI, 0.01-0.71; P = .04) and BNP (OR = 4.45; 95% CI, 1.1-17.9; P = .05) to be independently associated with CSA.

CONCLUSIONS

In patients with HF and CSA, leptin concentration is low and is inversely related to NP concentration. Counterregulatory interactions of leptin and NP may be important in ventilatory control in HF.

Neuronal control of breathing: sex and stress hormones

There is a growing public awareness that hormones can have a significant impact on most biological systems, including the control of breathing. This review will focus on the actions of two broad classes of hormones on the neuronal control of breathing: sex hormones and stress hormones. The majority of these hormones are steroids; a striking feature is that both groups are derived from cholesterol. Stress hormones also include many peptides which are produced primarily within the paraventricular nucleus of the hypothalamus (PVN) and secreted into the brain or into the circulatory system. In this article we will first review and discuss the role of sex hormones in respiratory control throughout life, emphasizing how natural fluctuations in hormones are reflected in ventilatory metrics and how disruption of their endogenous cycle can predispose to respiratory disease. These effects may be mediated directly by sex hormone receptors or indirectly by neurotransmitter systems. Next, we will discuss the origins of hypothalamic stress hormones and their relationship with the respiratory control system. This relationship is 2-fold: (i) via direct anatomical connections to brainstem respiratory control centers, and (ii) via steroid hormones released from the adrenal gland in response to signals from the pituitary gland. Finally, the impact of stress on the development of neural circuits involved in breathing is evaluated in animal models, and the consequences of early stress on respiratory health and disease is discussed.

Mechanical properties of the upper airway

The importance of the upper airway (nose, pharynx, and larynx) in health and in the pathogenesis of sleep apnea, asthma, and other airway diseases, discussed elsewhere in the Comprehensive Physiology series, prompts this review of the biomechanical properties and functional aspects of the upper airway. There is a literature based on anatomic or structural descriptions in static circumstances, albeit studied in limited numbers of individuals in both health and disease. As for dynamic features, the literature is limited to studies of pressure and flow through all or parts of the upper airway and to the effects of muscle activation on such features; however, the links between structure and function through airway size, shape, and compliance remain a topic that is completely open for investigation, particularly through analyses using concepts of fluid and structural mechanics. Throughout are included both historically seminal references, as well as those serving as signposts or updated reviews. This article should be considered a resource for concepts needed for the application of biomechanical models of upper airway physiology, applicable to understanding the pathophysiology of disease and anticipated results of treatment interventions.

Testosterone conversion blockade increases breathing stability in healthy men during NREM sleep

STUDY OBJECTIVES

Gender differences in the prevalence of sleep apnea/hypopnea syndrome may be mediated via male sex hormones. Our objective was to determine the exact pathway for a testosterone-mediated increased propensity for central sleep apnea via blockade of the 5α-reductase pathway of testosterone conversion by finasteride.

DESIGN

Randomization to oral finasteride vs. sham, single-center study.

SETTING

Sleep research laboratory.

PARTICIPANTS

Fourteen healthy young males without sleep apnea.

INTERVENTION

Hypocapnia was induced via brief nasal noninvasive positive pressure ventilation during stable NREM sleep. Cessation of mechanical ventilation resulted in hypocapnic central apnea or hypopnea.

MEASUREMENTS AND RESULTS

The apnea threshold (AT) was defined as the end-tidal CO₂(P(ET)CO₂) that demarcated the central apnea closest to the eupneic P(ET)CO₂. The CO₂ reserve was defined as the difference in P(ET)CO₂ between eupnea and AT. The apneic threshold and CO₂ reserve were measured at baseline and repeated after at a minimum of 1 month. Administration of finasteride resulted in decreased serum dihydrotestosterone. In the finasteride group, the eupneic ventilatory parameters were unchanged; however, the AT was decreased (38.9 ± 0.6 mm Hg vs.37.7 ± 0.9 mm Hg, P = 0.02) and the CO₂ reserve was increased (-2.5 ± 0.3 mm Hg vs. -3.8 ± 0.5 mm Hg, P = 0.003) at follow-up, with a significantly lower hypocapnic ventilatory response, thus indicating increased breathing stability during sleep. No significant changes were noted in the sham group on follow-up study.

CONCLUSIONS

Inhibition of testosterone action via the 5α-reductase pathway may be effective in alleviating breathing instability during sleep, presenting an opportunity for novel therapy for central sleep apnea in selected populations.

Central sleep apnea

Neurophysiologically, central apnea is due to a temporary failure in the pontomedullary pacemaker generating breathing rhythm. As a polysomnographic finding, central apneas occur in many pathophysiological conditions. Depending on the cause or mechanism, central apneas may not be clinically significant, for example, those that occur normally at sleep onset. In contrast, central apneas occur in a number of disorders and result in pathophysiological consequences. Central apneas occur commonly in high-altitude sojourn, disrupt sleep, and cause desaturation. Central sleep apnea also occurs in number of disorders across all age groups and both genders. Common causes of central sleep apnea in adults are congestive heart failure and chronic use of opioids to treat pain. Under such circumstances, diagnosis and treatment of central sleep apnea may improve quality of life, morbidity, and perhaps mortality. The mechanisms of central sleep apnea have been best studied in congestive heart failure and hypoxic conditions when there is increased CO2 sensitivity below eupnea resulting in lowering eupneic PCO2 below apneic threshold causing cessation of breathing until the PCO2 rises above the apneic threshold when breathing resumes. In many other disorders, the mechanism of central sleep apnea (CSA) remains to be investigated.

Drug effects on ventilatory control and upper airway physiology related to sleep apnea

Understanding the inter-relationship between pharmacological agents, ventilatory control, upper airway physiology and their consequent effects on sleep-disordered breathing may provide new directions for targeted drug therapy. Where available, this review focuses on human studies that contain both drug effects on sleep-disordered breathing and measures of ventilatory control or upper airway physiology. Many of the existing studies are limited in sample size or comprehensive methodology. At times, the presence of paradoxical findings highlights the complexity of drug therapy for OSA. The existing studies also highlight the importance of considering inter-individual pharmacokinetics and underlying causes of sleep apnea in interpreting drug effects on sleep-disordered breathing. Practical ways to assess an individual's ventilatory control and how it interacts with upper airway physiology is required for future targeted pharmacotherapy in sleep apnea.

The effects of testosterone on ventilatory responses in men with obstructive sleep apnea: a randomised, placebo-controlled trial

We recently showed that testosterone therapy worsens sleep-disordered breathing at 6-7 weeks, but not after 18 weeks, in men with obstructive sleep apnea. Changes in ventilatory chemoreflexes may be responsible. The effect of testosterone on ventilatory chemoreflexes in men with obstructive sleep apnea has not been systematically studied before. Twenty-one obese men with obstructive sleep apnea, a subgroup of our recent report, were randomised in an 18-week, randomised, double-blind, placebo-controlled, parallel group trial to three intramuscular injections (0, 6, 12 weeks) of either 1000 mg testosterone undecanoate (n = 10) or placebo (n = 11). Awake ventilatory chemoreflex testing was performed before (week 0), during (week 6) and at the end of treatment (week 18) to determine the ventilatory carbon dioxide recruitment threshold and chemosensitivity. Sleep and breathing was assessed by overnight polysomnography at 0, 7 and 18 weeks. Serum hormones levels were measured at every visit. A significant increase in blood testosterone levels (5.65 nmol L(-1) , 0.51-10.8 nmol L(-1) , P = 0.03) and lean muscle mass (2.36 kg, 0.8-3.9 kg, P = 0.007) between the two groups was observed as expected. No significant differences were seen in ventilatory chemoreflexes between the two groups at 6 weeks or at 18 weeks. However, positive correlations were observed between changes in serum testosterone and hyperoxic ventilatory recruitment threshold (r = 0.55, P = 0.03), and between changes in hyperoxic ventilatory recruitment threshold and time spent with oxygen saturations during sleep <90% (r = 0.57, P = 0.03) at 6-7 weeks, but not at 18 weeks. Time-dependent alterations in ventilatory recruitment threshold may therefore mediate the time-dependent changes in sleep breathing observed with testosterone.

Effects of testosterone therapy on sleep and breathing in obese men with severe obstructive sleep apnoea: a randomized placebo-controlled trial

STUDY OBJECTIVES

High doses of short-term testosterone have been shown to acutely worsen sleep-disordered breathing in men with obstructive sleep apnoea (OSA). The effects of lower, near-conventional doses of testosterone in obese men with OSA may differ over the longer term but have not been systematically studied. We assessed sleep and breathing effects of near-conventional testosterone treatment as an adjunct to weight loss in obese men with severe OSA.

DESIGN

An 18-week randomized, double-blind, placebo-controlled, parallel group trial in 67 men.

INTERVENTIONS

All subjects were placed on a hypocaloric diet and then received intramuscular injections of 1000 mg testosterone undecanoate or placebo at 0, 6 and 12 weeks.

MEASUREMENTS AND RESULTS

Sleep and breathing were measured by nocturnal polysomnography at 0, 7 and 18 weeks. Testosterone, compared to placebo, worsened the oxygen desaturation index (ODI) by 10·3 events/h (95%CI, 0·8-19·8 events/h; P = 0·03) and nocturnal hypoxaemia (sleep time with oxygen saturation <90%, SpO(2) T90%) by 6·1% (95%CI, 1·5-10·6; P = 0·01) at 7 weeks. Testosterone therapy did not alter ODI (4·5, -5·4 to 14·4 events/h; P = 0·36) or SpO(2) T90% at 18 weeks (2·9, -1·9-7·7%; P = 0·23) compared to placebo. The testosterone treatment effects on ODI and SpO(2) T90% were not influenced by baseline testosterone concentrations (testosterone by treatment interactions, all P > 0·35). Blood testosterone concentrations did not correlate with ODI or SpO(2) T90% (all P > 0·19).

CONCLUSIONS

Testosterone therapy in obese men with severe OSA mildly worsens sleep-disordered breathing in a time-limited manner, irrespective of initial testosterone concentrations. This time-dependency was not related to testosterone concentrations.

TRIAL REGISTRATION

www.anzctr.org.au Identifier: ACTRN1260-6000404527.

Effects of clonidine on breathing during sleep and susceptibility to central apnoea

We hypothesized that administration of clonidine would decrease the hypocapnic apnoeic threshold (HAT) and widen the CO(2) reserve during non-REM sleep.

METHODS

Ten healthy subjects (4 females) (age 22.3 ± 3.0 years; BMI 25.5 ± 3.4 kg/m(2)) were randomized to receive placebo or 0.1 mg/45 kg of clonidine on 2 separate nights. Ventilation and upper airway resistance were monitored during wakefulness and sleep. Two separate experiments were performed: Protocol 1 (n=8), CO(2) reserve, HAT and HcVR were determined using non-invasive hyperventilation (NIV) to induce hypocapnia for at least 3 min; Protocol 2 (n=6), peripheral hypocapnic ventilatory response (HcVR) was determined by NIV using short (3 breaths) hyperventilation.

RESULTS

Clonidine decreased the systolic blood pressure by 12 ± 10 mmHg but did not affect baseline ventilation or upper airway resistance during wakefulness or sleep. Protocol (1), clonidine was associated with decreased HAT relative to placebo (37.3 ± 3.3 mmHg vs. 39.7 ± 3.4 mmHg, P<0.05), increased CO(2) reserve (-3.8 ± 1.3 mmHg vs. -2.8 ± 1.2 mmHg, P<0.05), and decreased HcVR (1.6 ± 0.6 L/min/mmHg vs. 2.5 ± 1.3 L/min/mmHg, P<0.05). Protocol (2), administration of clonidine did not decrease peripheral HcVR compared to placebo (0.5 ± 0.3 L/min/mmHg vs. 0.7 ± 0.3 L/min/mmHg, P=NS).

CONCLUSION

Clonidine is associated with diminished susceptibility to hypocapnic central apnoea without significant effect on ventilation or upper airway mechanics. Reduced susceptibility to hypocapnic central apnoea is not explained by the peripheral chemoreceptor pathway. This suggests a central rather than a peripheral effect of clonidine on the susceptibility to hypocapnic central apnoea.

Metabolic dysfunction in pcos: Relationship to obstructive sleep apnea

Polycystic ovary syndrome (PCOS) affects between 5% and 8% of women, making it one of the most common endocrinopathies in women. The disorder typically has its onset at puberty with evidence of excessive androgen production, obesity, and insulin resistance. Women with PCOS are more insulin resistant than weight-matched controls and have an exceptionally high prevalence of early-onset impaired glucose tolerance (30-40%), and type 2 diabetes (up to 10%). Over the past several years, chronic decreases in sleep duration and/or quality have been identified as a risk for the development of a number of metabolic derangements that are strikingly similar to those seen in PCOS. Specifically, decreased sleep quality due to obstructive sleep apnea (OSA) has been causally linked to insulin resistance, glucose intolerance, dyslipidemia and hypertension independent of body mass index (BMI). Until recently, however, it had not been recognized that OSA is present in a disproportionate number of women with PCOS: the risk for OSA is at least 5- to 10-fold higher compared to the risk in similarly obese women without PCOS. The causes and consequences of OSA in women with PCOS are addressed in this manuscript.

The association of testosterone, sleep, and sexual function in men and women

Testosterone has been the focus of several investigations and review studies in males, but few have addressed its effects on sleep and sexual function, despite evidence of its androgenic effects on circadian activity in both sexes. Studies have been conducted to understand how sleeping increases (and how waking decreases) testosterone levels and how this rhythm can be related to sexual function. This review addresses the inter-relationships among testosterone, sexual function and sleep, including sleep-disordered breathing in both sexes, specifically its effects related to sleep deprivation. In addition, hormonal changes in testosterone that occur in the gonadal and adrenal axis with obstructive sleep apnea and other conditions of chronic sleep deprivation, and which consequently affect sexual life, have also been explored. Nevertheless, hormone-associated sleep disruptions occur across a lifetime, particularly in women. The association between endogenous testosterone and sex, sleep and sleep disturbances is discussed, including the results of clinical trials as well as animal model studies. Evidence of possible pathophysiological mechanisms underlying this relationship is also described. Unraveling the associations of sex steroid hormone concentrations with sleep and sexual function may have clinical implications, as sleep loss reduces testosterone levels in males, and low sex steroid hormone concentrations have been associated with sexual dysfunction.

Hypocapnia is associated with increased upper airway expiratory resistance during sleep

We hypothesized that hypocapnia is responsible for increased expiratory resistance during NREM sleep. Hypocapnia was induced by hypoxic hyperventilation in 21 subjects (aged 29.4 ± 7.8 yrs, 10 women, BMI 24.4 ± 4.3 kg/m(2)). Isocapnic hypoxia was induced in 12 subjects of whom, 6 underwent hypocapnic hypoxia in the same night. Upper airway resistance (R(UA)) was measured at the linear pressure-flow relationship during inspiration and expiration. Inspiratory flow limitation (IFL) was defined as the dissociation in pressure-flow relationship. (1) Expiratory R(UA) increased during hypocapnic but not isocapnic hypoxia relative to control (11.0 ± 5.6 vs. 8.2 ± 3.6 cm H(2)O/L/s; p < 0.05, and 11.45.0 vs. 10.94.4 cm H(2)O/L/s; p = NS, respectively). (2) No gender difference was found in R(UA) (p = NS). (3) Increased expiratory R(UA) correlated with the IFL change during hypocapnic but not isocapnic hypoxia. (4) No changes were noted in inspiratory R(UA) or IFL. Expiratory R(UA) increased during hypocapnia and was associated with IFL, indicating upper airway narrowing. Gender does not influence the upper airway response to hypocapnic hypoxia.

Inhibition of ventilatory motor output increases expiratory retro palatal compliance during sleep

We hypothesized that inhibition of ventilatory motor output leads to increased pharyngeal compliance during NREM sleep, independent of lung volume.

METHODS

Eighteen subjects were studied using noninvasive positive pressure ventilation (NPPV) to inhibit ventilatory motor output during stable NREM sleep. Nasopharyngoscopy was used to measure the retro palatal cross-sectional area/pressure relationship (CSA/Pph) in 8 subjects. The effect of NPPV on neck circumference (NC) and end-expiratory lung volumes (EELV) was studied in 10 additional subjects using strain gauge plethysmography and respitrace, respectively.

RESULTS

(1) The CSA/Pph was increased during expiration under passive compared to active breathing (11.7 ± 7.1 vs. 8.5 ± 5.6mm(2)/cmH(2)O, respectively; p < 0.05) but not during inspiration. (2) NC correlated with the CSA/Pph during passive expiration (R(2) = 0.77, p < 0.05). (3) NC and EELV did not change between active and passive breaths (p = NS).

CONCLUSIONS

(1) Inhibiting the ventilatory motor output increases the pharyngeal compliance. (2) Increased passive expiratory pharyngeal compliance was not associated with changes in NC or EELV.